Simply locate Bartholomew (for those of you who don't know who he is, he is the man on the far left of the painting). Now look above his head at the pillar and you will see something truly amazing. The dagger, or the Graille, was suspected of being the Holy Grail, but was simply showing that Da Vinci wasn't happy with the shape of the mans belly and put in the Graille to show that he wanted it smaller. (A Graille being a filing device) The Grail has been searched for by many for many years. It is so obvious yet so hidden. Amazing huh?!